Add ReverseDiff support.

[tpapp]

No description provided.

[codecov]

Codecov Report

Merging #23 into master will increase coverage by 12.14%.
The diff coverage is 66.66%.

@@           Coverage Diff            @@
##           master   #23       +/-   ##
========================================
+ Coverage   72.85%   85%   +12.14%     
========================================
  Files           3     4        +1     
  Lines          70    80       +10     
========================================
+ Hits           51    68       +17     
+ Misses         19    12        -7

Impacted Files	Coverage Δ
src/AD_ForwardDiff.jl	80% <0%> (+8.57%)	⬆️
src/LogDensityProblems.jl	89.13% <50%> (+8.17%)	⬆️
src/AD_ReverseDiff.jl	85.71% <85.71%> (ø)
src/AD_Flux.jl	71.42% <0%> (+42.85%)	⬆️

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[coveralls]

Pull Request Test Coverage Report for Build 87

• 7 of 10 (70.0%) changed or added relevant lines in 3 files are covered.
• 3 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+10.3%) to 83.117%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/AD_ForwardDiff.jl	0	1	0.0%
src/AD_ReverseDiff.jl	6	7	85.71%
src/LogDensityProblems.jl	1	2	50.0%

Files with Coverage Reduction	New Missed Lines	%
src/LogDensityProblems.jl	3	86.36%

Totals
Change from base Build 84:	10.3%
Covered Lines:	64
Relevant Lines:	77

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💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 93

• 8 of 12 (66.67%) changed or added relevant lines in 3 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage increased (+10.7%) to 83.544%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/AD_ForwardDiff.jl	0	1	0.0%
src/AD_ReverseDiff.jl	6	7	85.71%
src/LogDensityProblems.jl	2	4	50.0%

Files with Coverage Reduction	New Missed Lines	%
src/LogDensityProblems.jl	1	86.96%

Totals
Change from base Build 84:	10.7%
Covered Lines:	66
Relevant Lines:	79

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💛 - Coveralls